This invention generally relates to medical devices for drainage of fluids, and more specifically to ureteral stents.
Ureteral stents are used to assist urinary drainage from the kidney to the urinary bladder in patients with a ureteral obstruction or injury, or to protect the integrity of the ureter in a variety of surgical manipulations. Stents may be used to treat or avoid ureteral obstructions (such as ureteral stones or ureteral tumors) which disrupt the flow of urine from the kidneys to the bladder. Serious obstructions may cause urine to back up into the kidneys, threatening renal function. Ureteral stents may also be used after endoscopic inspection of the ureter to prevent obstruction of the ureter by swelling of the ureteral wall caused by the surgical procedure.
Ureteral stents typically are tubular in shape, terminating in two opposing ends: a kidney distal end and a bladder proximal end. One or both of the ends may be coiled in a pigtail or J-shape to prevent the upward and/or downward migration of the stent due, for example, to physiological movements. A kidney end coil resides within the lumen of the kidney, known as the renal pelvis, and is designed to prevent stent migration down the ureter and into the bladder. The bladder-end coil resides in the bladder and is designed to prevent stent migration upward toward the kidney. The bladder coil is also used to aid in retrieval and removal of the stent. Regions such as the trigone region in the bladder and the region of the ureter near the bladder known as the ureteral-vesical junction are particularly sensitive to irritation by foreign objects. Commonly used bladder-end coils contact and irritate the trigone region causing discomfort to the patient. Similarly, the proximal region of the stent contacts the ureteral-vesical junction causing irritation and discomfort to the patient particularly during voiding. Additionally, ureteral stents, particularly the portion positioned within the ureteral-vesical junction and inside the bladder, may produce adverse effects including blood in the urine, a continual urge to urinate, strangury, and flank pain accompanying reflux of urine up the stent (e.g., when voiding). Such effects occur as pressure within the bladder is transmitted to the kidney. In short, while providing drainage from the kidney to the bladder, stents may also cause or contribute to significant patient discomfort and serious medical problems.
The present invention relates to a ureteral stent that reduces patient discomfort and urine reflux. In particular, the invention relates to a foam segment, disposed at the proximal end of the stent, which reduces urine reflux and minimizes contact with the trigone region and ureteral-vesical junction. When the stent is placed within the urinary system of a patient, the foam segment is located within the ureteral-vesical junction, and also in the bladder itself. The foam segment, constructed from a soft and compressible open-cell or reticulated foam material, for example, minimizes the amount of irritation to the ureteral-vesical junction and the trigone region. Also, the foam segment, which is present within or blocks the opening of the stent lumen, partially occludes the stent lumen. This partial occlusion of the lumen prevents the rapid flow of urine through the stent to the kidney during urine reflux.
The foam segment also forms a proximal retention structure that is positioned in the urinary bladder when the stent is in use and functions to restrain the migration of the stent towards the kidney. The stent also includes a distal retention structure, which when the stent is installed in the patient, is generally located in the renal pelvis and functions to prevent the migration of the stent down the ureter into the urinary bladder.
In one aspect, the invention relates to a ureteral stent that includes an elongated member that defines a lumen extending therethrough, a distal retention structure that is defined by a distal region of the elongated member, and a foam segment that extends from a proximal end of the elongated member and is in fluid communication with the lumen.
In one embodiment, the foam segment includes a proximal retention structure. The proximal retention structure prevents the migration of the stent upward towards a kidney. In another embodiment, a distal portion of the foam segment is contained within the lumen of the elongated member. In yet another embodiment, a portion of the foam segment is attached to an outer surface of a proximal end of the elongated member. In further embodiments, the foam segment may include an open-cell foam, a reticulated foam, or a closed-cell foam.
In another embodiment, an outer dimension of the proximal retention structure that is substantially perpendicular to a longitudinal axis of the elongated member is larger than the diameter of the elongated member. A proximal retention structure with such an outer dimension prevents the proximal retention structure from entering into a ureter. In various embodiments, the proximal retention structure may include a funnel shape, a conical shape or a spherical shape, for example. In yet another embodiment, an outer dimension of the distal retention structure that is substantially perpendicular to a longitudinal axis of the elongated member is larger than the diameter of the elongated member. A distal retention structure with such an outer dimension prevents the distal retention structure from entering into a ureter. In one embodiment the distal retention structure includes a coiled shape.
In one embodiment, the elongated member of the ureteral stent includes an outer diameter ranging from about 6 to about 12 French. In another embodiment, the elongated member may include a biocompatible plastic.
In one embodiment of the invention, the foam segment further includes a coaxial member that defines a lumen extending therethrough. The coaxial member is fixed within the foam segment, by a bonding process, for example. In another embodiment, the foam segment of the ureteral stent defines a lumen extending therethrough.
In another aspect, the invention relates to a method for draining urine from a kidney. The method first requires providing a ureteral stent such as previously described. The stent is then inserted into a ureter of a patient. In one embodiment, the stent is positioned such that at least a portion of the distal retention structure resides within a kidney. In another embodiment, the stent is positioned such that at least a portion of the foam segment of the stent resides within a ureteral-vesical junction. In another embodiment, the foam segment includes a proximal retention structure. The proximal retention structure is positioned in the bladder thus preventing the migration of the proximal end of the stent out of a urinary bladder.
In another aspect, the invention relates to a method of positioning a ureteral stent within a patient. The method includes providing a ureteral stent as previously described. The method then includes positioning the stent within a patient using a guide wire and a pusher. First, the stent is mounted over a guide wire already positioned within the body and then is pushed along the guide wire utilizing a pusher to locate the stent within the ureter of a patient. The shape of the pusher, particularly the distal end of the pusher, conforms to a shape of a proximal end of the ureteral stent. This allows the pusher to effectively transfer the necessary force to the proximal end of the stent to position the stent within the patient. Once the stent is properly located within patient, the guide wire is removed from the patient. The pusher may also be removed from the patient after the procedure.
In one embodiment, the method further includes inserting the guide wire into a urinary tract of the patient. The guide wire may be inserted into the urinary tract prior to inserting the stent into the urinary tract. In another embodiment, the method further includes positioning the distal retention structure within a kidney. The distal retention structure prevents the stent from migrating down the ureter and into the urinary bladder. In yet another embodiment, the foam segment of the stent includes a proximal retention structure, and the method further includes positioning the proximal retention structure in a urinary bladder. The proximal retention structure prevents the stent from migrating out of the bladder and up the ureter. In yet another embodiment, mounting the stent over a guide wire includes inserting the guide wire within a lumen of the elongated member.
The foregoing and other aspects, embodiments, features, and advantages of the invention will become apparent from the following description, figures, and claims.